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Cryo-EM structure of the bacteriophage T4 portal protein assembly at near-atomic resolution.

Sun L, Zhang X, Gao S, Rao PA, Padilla-Sanchez V, Chen Z, Sun S, Xiang Y, Subramaniam S, Rao VB, Rossmann MG - Nat Commun (2015)

Bottom Line: However, the detailed structure of the portal protein remained unknown.The gp20 structure also verifies that the portal assembly is required for initiating head assembly, for attachment of the packaging motor, and for participation in DNA packaging.Comparison of the Myoviridae T4 portal structure with the known portal structures of φ29, SPP1 and P22, representing Podo- and Siphoviridae, shows that the portal structure probably dates back to a time when self-replicating microorganisms were being established on Earth.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Purdue University, 240S. Martin Jischke Drive, West Lafayette, Indiana 47907-2032, USA.

ABSTRACT
The structure and assembly of bacteriophage T4 has been extensively studied. However, the detailed structure of the portal protein remained unknown. Here we report the structure of the bacteriophage T4 portal assembly, gene product 20 (gp20), determined by cryo-electron microscopy (cryo-EM) to 3.6 Å resolution. In addition, analysis of a 10 Å resolution cryo-EM map of an empty prolate T4 head shows how the dodecameric portal assembly interacts with the capsid protein gp23 at the special pentameric vertex. The gp20 structure also verifies that the portal assembly is required for initiating head assembly, for attachment of the packaging motor, and for participation in DNA packaging. Comparison of the Myoviridae T4 portal structure with the known portal structures of φ29, SPP1 and P22, representing Podo- and Siphoviridae, shows that the portal structure probably dates back to a time when self-replicating microorganisms were being established on Earth.

No MeSH data available.


Related in: MedlinePlus

Cryo-EM reconstruction of the T4 prolate head at 10 Å resolution.(a,b) Cryo-EM density map of the T4 prolate head (gp23: cyan; gp24:magenta; Soc: pink; Hoc: yellow). (c) Bottom view of the prolate head, showing the gap between gp20 and the capsid. (d) Fit of the gp20 and gp23 structures into the cryo-EM map of the T4 prolate head. (e) A model of the T4 head assembly. A dodecameric portal is assembled on the inner membrane of E. coli with the assistance of the phage-coded chaperone gp40 and the E. coli chaperone YidC58. The portal assembly acts as an initiator for head assembly, leading to co-polymerization of the major capsid protein gp23 and scaffolding proteins.
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f3: Cryo-EM reconstruction of the T4 prolate head at 10 Å resolution.(a,b) Cryo-EM density map of the T4 prolate head (gp23: cyan; gp24:magenta; Soc: pink; Hoc: yellow). (c) Bottom view of the prolate head, showing the gap between gp20 and the capsid. (d) Fit of the gp20 and gp23 structures into the cryo-EM map of the T4 prolate head. (e) A model of the T4 head assembly. A dodecameric portal is assembled on the inner membrane of E. coli with the assistance of the phage-coded chaperone gp40 and the E. coli chaperone YidC58. The portal assembly acts as an initiator for head assembly, leading to co-polymerization of the major capsid protein gp23 and scaffolding proteins.

Mentions: A three-dimensional, cryo-EM structure of the mature T4 prolate head-plus-tail had been determined to 22 Å resolution using fivefold symmetry17. In addition, the structure of the prolate prohead with the attached packaging motor had been determined to 35 Å resolution using fivefold symmetry6. Here we also report a 10 Å resolution reconstruction of an emptied prolate head, determined by imposing fivefold symmetry. All these reconstructions show the small outer capsid protein (Soc) molecules surrounding the major capsid protein (gp23) hexamers and the highly antigenic outer capsid protein (Hoc) molecules protruding from the centre of the hexamers1820 (Fig. 3a). Furthermore the fivefold vertices are occupied by gp24 pentamers. The special vertex is missing this pentameric unit and instead contains the portal assembly. Because of the 12-fold to 5-fold symmetry mismatch between the portal and capsid, respectively, there remains uncertainty about the relative rotational orientation of the portal with respect to the capsid. Thus, the cryo-EM density representing the portal in the prolate head is the average of many orientations and, therefore, represents the envelope of the portal assembly. A model of the major capsid protein, gp23, derived from a 5.6 Å resolution reconstruction of an isometric T4 mutant (Z. Chen, Z. Zhang, L. Sun, M. G. Rossmann, V. B. Rao, manuscript in preparation) was used to interpret the structure of the prolate head.


Cryo-EM structure of the bacteriophage T4 portal protein assembly at near-atomic resolution.

Sun L, Zhang X, Gao S, Rao PA, Padilla-Sanchez V, Chen Z, Sun S, Xiang Y, Subramaniam S, Rao VB, Rossmann MG - Nat Commun (2015)

Cryo-EM reconstruction of the T4 prolate head at 10 Å resolution.(a,b) Cryo-EM density map of the T4 prolate head (gp23: cyan; gp24:magenta; Soc: pink; Hoc: yellow). (c) Bottom view of the prolate head, showing the gap between gp20 and the capsid. (d) Fit of the gp20 and gp23 structures into the cryo-EM map of the T4 prolate head. (e) A model of the T4 head assembly. A dodecameric portal is assembled on the inner membrane of E. coli with the assistance of the phage-coded chaperone gp40 and the E. coli chaperone YidC58. The portal assembly acts as an initiator for head assembly, leading to co-polymerization of the major capsid protein gp23 and scaffolding proteins.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4493910&req=5

f3: Cryo-EM reconstruction of the T4 prolate head at 10 Å resolution.(a,b) Cryo-EM density map of the T4 prolate head (gp23: cyan; gp24:magenta; Soc: pink; Hoc: yellow). (c) Bottom view of the prolate head, showing the gap between gp20 and the capsid. (d) Fit of the gp20 and gp23 structures into the cryo-EM map of the T4 prolate head. (e) A model of the T4 head assembly. A dodecameric portal is assembled on the inner membrane of E. coli with the assistance of the phage-coded chaperone gp40 and the E. coli chaperone YidC58. The portal assembly acts as an initiator for head assembly, leading to co-polymerization of the major capsid protein gp23 and scaffolding proteins.
Mentions: A three-dimensional, cryo-EM structure of the mature T4 prolate head-plus-tail had been determined to 22 Å resolution using fivefold symmetry17. In addition, the structure of the prolate prohead with the attached packaging motor had been determined to 35 Å resolution using fivefold symmetry6. Here we also report a 10 Å resolution reconstruction of an emptied prolate head, determined by imposing fivefold symmetry. All these reconstructions show the small outer capsid protein (Soc) molecules surrounding the major capsid protein (gp23) hexamers and the highly antigenic outer capsid protein (Hoc) molecules protruding from the centre of the hexamers1820 (Fig. 3a). Furthermore the fivefold vertices are occupied by gp24 pentamers. The special vertex is missing this pentameric unit and instead contains the portal assembly. Because of the 12-fold to 5-fold symmetry mismatch between the portal and capsid, respectively, there remains uncertainty about the relative rotational orientation of the portal with respect to the capsid. Thus, the cryo-EM density representing the portal in the prolate head is the average of many orientations and, therefore, represents the envelope of the portal assembly. A model of the major capsid protein, gp23, derived from a 5.6 Å resolution reconstruction of an isometric T4 mutant (Z. Chen, Z. Zhang, L. Sun, M. G. Rossmann, V. B. Rao, manuscript in preparation) was used to interpret the structure of the prolate head.

Bottom Line: However, the detailed structure of the portal protein remained unknown.The gp20 structure also verifies that the portal assembly is required for initiating head assembly, for attachment of the packaging motor, and for participation in DNA packaging.Comparison of the Myoviridae T4 portal structure with the known portal structures of φ29, SPP1 and P22, representing Podo- and Siphoviridae, shows that the portal structure probably dates back to a time when self-replicating microorganisms were being established on Earth.

View Article: PubMed Central - PubMed

Affiliation: Department of Biological Sciences, Purdue University, 240S. Martin Jischke Drive, West Lafayette, Indiana 47907-2032, USA.

ABSTRACT
The structure and assembly of bacteriophage T4 has been extensively studied. However, the detailed structure of the portal protein remained unknown. Here we report the structure of the bacteriophage T4 portal assembly, gene product 20 (gp20), determined by cryo-electron microscopy (cryo-EM) to 3.6 Å resolution. In addition, analysis of a 10 Å resolution cryo-EM map of an empty prolate T4 head shows how the dodecameric portal assembly interacts with the capsid protein gp23 at the special pentameric vertex. The gp20 structure also verifies that the portal assembly is required for initiating head assembly, for attachment of the packaging motor, and for participation in DNA packaging. Comparison of the Myoviridae T4 portal structure with the known portal structures of φ29, SPP1 and P22, representing Podo- and Siphoviridae, shows that the portal structure probably dates back to a time when self-replicating microorganisms were being established on Earth.

No MeSH data available.


Related in: MedlinePlus